Conventional wetting agents can lower the surface tension attainable for an aqueous solution to between 25 and 27 dynes/cm. It has long been known that synergistic mixtures of surfactants can lower this minimum surface tension still further to between 22 and 24 dynes/cm (Miles et al. J. Phys. Chem. 48, 57 (1944)). Similarly, fluoroaliphatic surfactants, hereafter referred to as R.sub.f -surfactants, can reduce the surface tension of an aqueous solution to between 15 and 20 dynes/cm. Similar synergistic effects can be attained with mixtures of R.sub.f -surfactants and conventional fluorine-free surfactants as first shown in 1954 by Klevens and Raison (Klevens et al, J. Chem. Phys. 51, 1 (1954)) and Bernett and Zisman (Bernett et al, J. Phys. Chem. 65, 448 (1961)).
Aqueous solutions which have surface tensions below the critical surface tension of wetting of a hydrocarbon or polar solvent surface, will spread spontaneously on such a surface. As a practical utilization of this principle, Tuve et al disclosed in U.S. Pat. No. 3,258,423 that specific R.sub.f -surfactants and R.sub.f -surfactant mixtures alone or in combination with solvents and other additives could be used as efficient fire fighting agents. Based on the Tuve et al findings, numberous fire fighting agents containing different R.sub.f -surfactants have been disclosed as for example U.S. Pat. Nos. 3,315,326, 3,475,333, 3,562,156, 3,655,555, 3,661,776, and 3,772,195; Brit. Pat. Nos. 1,070,289, 1,230,980, 1,245,124, 1,270,662, 1,280,508, 1,381,953; Ger. Pat. Nos. 2,136,424, 2,165,057, 2,240,263, 2,315,326; Can. Pat. Nos. 842,252, and pending U.S. Application Ser. No. 561,393.
Fire fighting agents containing R.sub.f -surfactants act in two ways:
A. As foams, they are used as primary fire extinguishing agents.
B. As vapor sealants, they prevent the re-ignition of fuel and solvents.
It is this second property which makes fluorochemical fire fighting agents far superior to any other known fire fighting agent for fighting fuel and solvent fires.
These R.sub.f -surfactant fire fighting agents are commonly known as AFFF (standing for Aqueous Film Forming Foams). AFFF agents act the way they do because the R.sub.f -surfactants reduce the surface tension of aqueous solutions to such a degree that the solutions will wet and spread upon non-polar and water immiscible solvents even though such solvents are lighter than water; they form a fuel or solvent vapor barrier which will rapidly extinguish flames and prevent re-ignition and reflash. The criterion necessary to attain spontaneous spreading of two immiscible phases has been taught by Hardins et al J. Am. Chem. 44, 2665 (1922). The measure of the tendency for spontaneous spreading is defined by the spreading coefficient (SC) as follows: EQU SC = .delta.a - .delta.b - .delta.i
where
Sc = spreading coefficient PA1 .delta.a = surface tension of the lower liquid phase PA1 .delta.b = surface tension of the upper aqueous phase PA1 .delta.i = interfacial tension between the aqueous upper phase and lower liquid phase. PA1 A. 0.5 to 25% by weight of a fluorinated surfactant, PA1 B. 0.1 to 5% by weight of a fluorinated synergist, PA1 C. 0.1 to 25% by weight of an ionic non-fluorochemical surfactant, PA1 D. 0.1 to 40% by weight of a nonionic hydrocarbon surfactant, PA1 E. 0 to 70% by weight of solvents, PA1 F. 0 to 5% by weight of an electrolyte, and PA1 G. water in the amount to make up the balance of 100% PA1 A. 1 to 3.5% by weight of fluorinated surfactant, PA1 B. 0.1 to 2.0% by weight of fluorinated synergist, PA1 C. 0.1 to 5.0% by weight of ionic non-fluorochemical surfactant, PA1 D. 0.1 to 4.0% by weight of nonionic hydrocarbon surfactant, PA1 E. 0 to 25.0% by weight of solvent, PA1 F. 0 to 2.0% by weight of electrolyte, and PA1 G) water in the amount to make up the balance of 100%. PA1 Surface Tension and Interfacial Tension -- ASTM D-1331-56 PA1 Freezing Point -- ASTM D-1177-65 PA1 pH -- ASTM D-1172
If the SC is positive, the surfactant solution should spread and film formation should occur. The greater the SC, the greater the spreading tendency. This requires the lowest possible aqueous surface tension and lowest interfacial tension, as is achieved with mixtures of certain R.sub.f -surfactants(s) and classical hydrocarbon surfactant mixtures.
Commercial AFFF agents are primarily used today in so-called 6% and 3% proportioning systems 6% means that 6 parts of an AFFF agent and 94 parts of water (fresh sea, or brackish water) are mixed or proportioned and applied by conventional foam making equipment wherever needed. Similarly an AFFF agent for 3% proportioning is mixed in such a way that 3 parts of this agent and 97 parts of water are mixed and applied.
Today AFFF agents are used wherever the danger of fuel solvent fires exist and expecially where expensive equipment has to be protected. They can be applied in many ways, generally using conventional portable handline foam nozzles, but also by other techniques such as with oscillating turret foam nozzles, subsurface injection equipment (petroleum tank farms), fixed non-aspirating sprinkler systems (chemical process areas, refineries), underwing and overhead hangar deluge systems, inline proportioning systems (induction metering devices), or aerosol type dispension units as might be used in a home or vehicle. AFFF agents are recommended fire suppressants for Class A or Class B flammable solvent fires, particularly the latter. Properly used alone or in conjunction with dry chemical extinguishing agents (twin-systems) they generate a vapor-blanketing foam with remarkable securing action.
AFFF agents generally have set a new standard in the fighting of fuel fires and surpass by far any performance of the previously used protein foams. However, the performance of today's commercial AFFF agents is not the ultimate as desired by the industry. The very high cost of AFFF agents is limiting a wider use and it is, therefore, mandatory that more efficient AFFF agents which require less fluorochemicals to achieve the same effect are developed. Furthermore, it is essential that secondary properties of presently available AFFF agents be improved. Prior art AFFF compositions are deficient with respect to a number of important criteria which severely limit their performance. The subject AFFF agents show marked improvements in the following respects:
Seal Speed and Persistence -- these important criteria equate to control, extinguishing, and burnback times of actual fire tests. The described AFFF agents spread rapidly on fuels and not only seal the surface from further volatilization and ignition, but maintain their excellent sealing capacity for long periods of time. The persistence of the seal with the subject compositions is considerably better than prior art formulations.
Preferred compositions spread rapidly and have a persistent seal even at lower than recommended use concentrations. At concentrations down to one-half the recommended dilutions, and even with sea water, which is generally a difficult diluent, seals are still attained rapidly and maintained considerably longer than by competitive AFFF agents. This built in safety factor for performance is vital when we consider how difficult it is to proportion precisely.
One must remember that in fire-fighting, lives are frequently at stake, and on stress situations the firefighter may err with regard to ideal proportioning of the concentrate. Even at one-half the designated dilution the subject compositions perform well.
Storage Stability -- the subject AFFF concentrates and premix solutions in sea water and hard water (300 ppm or greater) maintain both clarity and foam expansion stability. No decrease is seen in performance after accelerated aging for over 40 days at 150.degree. F). Prior art compsitions were noticeably inferior upon accelerated aging in that clarity could not be maintained, and the foam expansion of premixes generally decreased.
Fluorine Efficiency -- substantial economics are realized because the subject AFFF compositions perform so well yet contain considerably less of the expensive fluorochemicals than do prior art formulations. Extremely low surface tensions and hence higher spreading coefficients, can be achieved with certain of the preferred AFFF compositions at very low fluorine levels.
Economics -- the preferred compositions can be prepared from relatively cheap and synthetically accessible fluorochemicals. The preferred fluorochemicals are conventional R.sub.f -surfactants, obtainable in extremely high yield by simple procedures adaptable to scale-up. The subject AFFF compositions are therefore economically competitive with available AFFF agents and may well permit the use of AFFF type firefighting compositions in hazardous application areas where lives and equipment can be protected but where their previous high price precluded their use. The AFFF agents of this invention also have: (a) a chloride content below 50 ppm so that the concentrate does not induce stress corrosion in stainless steel, and (b) such a high efficiency that instead of using 3 and 6% proportioning systems it is possible to use AFFF agents in 1% or lower proportioning systems. This means that 1 part of an AFFF agent can be blended or diluted with 99 parts of water. Such highly efficient concentrates are of importance because storage requirements of AFFF agents can be greatly reduced, or in the case where storage facilities exist, the capacity of available fire protection agent will be greatly increased. AFFF agents for 1% proportioning systems are of great importance therefore wherever storage capacity is limited such as on offshore oil drilling rigs, offshore atomic power stations, city fire trucks and so on. The performance expected from an AFFF agent today is in most countries regulated by the major users such as the military and the most important AFFF specifications are documented in the U.S. Navy Military Specification MIL-F-24385 and its subsequent amendments.
The novel AFFF agents described of this invention are in comparison with today's AFFF agents superior not only with regard to the primary performance characteristics such as control time, extinguishing time and burnback resistance but additionally, because of their very high efficiency offer the possibility of being used in 1% proportioning systems. Furthermore, they offer desirable secondary properties from the standpoint of ecology as well as economy.
Detailed Disclosure -- The present invention is directed to aqueous film forming concentrate compositions for 1 to 6% proportioning, for extinguishing or preventing fires by suppressing the vaporization of flammable liquids, said composition comprising
Each component A to F may consist of a specific compound or a mixture of compounds.
The above composition is a concentrate which, as noted above, when diluted with water, forms a very effective fire fighting formulation by forming a foam which deposits a tough film over the surface of the flammable liquid which prevents its further vaporization and thus extinguishes the fire.
It is a preferred fire extinguishing agent for flammable solvent fires, particularly for hydrocarbons and polar solvents of low water solubility, in particular for:
Hydrocarbon Fuels -- such as gasoline, heptane, toluene, hexane, Avgas, VMP naphtha, cyclohexane, turpentine, and benzene;
Polar Solvents of Low Water Solubility -- such as butyl acetate, methyl isobutyl ketone, butanol, ethyl acetate, and
Polar Solvents of High Water Solubility -- such as methanol, acetone, isopropanol, methyl ethyl ketone, ethyl cellosolve and the like.
It may be used concomitantly or successively with flame suppressing dry chemical powders such as sodium or potassium bicarbonate, ammonium dihydrogen phosphate, CO.sub.2 gas under pressure, or Purple K, as in so-called Twin-agent systems. A dry chemical to AFFF agent ratio would be from 10 to 30 lbs of dry chemical to 2 to 10 gallons AFFF agent at use concentration (i.e. after 0.5%, 1%, 3%, 6% or 12% proportioning). In a typical example 20 lbs of a dry chemical and 5 gals. of AFFF agent could be used. The composition of this invention could also be used in conjunction with hydrolyzed protein or fluoroprotein foams.
The foams of the instant invention do not disintegrate or otherwise adversely react with a dry powder such as Purple-K Powder (P-K-P). Purple-K Powder is a term used to designate a potassium bicarbonate fire extinguishing agent which is free-flowing and easily sprayed as a powder cloud on flammable liquid and other fires.
The concentrate is normally diluted with water by using a proportioning system such as, for example, a 3% or 6% proportioning system whereby 3 parts or 6 parts of the concentrate is admixed with 97 or 94 parts respectively of water. This highly diluted aqueous composition is then used to extinguish and secure the fire.
The fluorinated surfactants employed in the compositions of this invention as component (A) may be chosen from among anionic, amphoteric or cationic surfactants, but preferred are anionic R.sub.f -surfactants represented by the formula ##STR1## where R.sub.f is straight or branched chain perfluoroalkyl of 1 to 18 carbon atoms or perfluoroalkyl substituted by perfluoroalkoxy of 2 to 6 carbon atom; R.sub.1 is hydrogen or lower alkyl; each of R.sub.2, R.sub.4 and R.sub.5 is individually hydrogen or alkyl group of 1-12 carbons; R.sub.3 is hydrogen, alkyl of 1 to 12 carbons, phenyl, tolyl, and pyridyl; R.sub.6 is branched or straight chain alkylene of 1 to 12 carbon atoms, alkylenethioalkylene of 2 to 12 carbon atoms, alkyleneoxyalkylene of 2 to 12 carbon atoms or alkyleneiminoalkylene of 2 to 12 carbon atoms where the nitrogen atom is secondary or tertiary; M is hydrogen, a monovalent alkali metal, an alkaline earth metal, an organic base or ammonium; and n is an integer corresponding to the valency of M, i.e., 1 or 2. The above R.sub.f -surfactant is disclosed in the copending U.S. Application Ser. No. 642,271 disclosure is incorporated herein by reference.
These preferred anionics are illustrated in Table 1 a, as are numerous other anionics useful purposes of this invention. A preferred group of amphoterics are disclosed more fully in the copending application of Karl F. Mueller, filed Jan. 3, 1975, Ser. No. 538,432 which is incorporated herein by reference, and are illustrated in Table 1b. Other amphoterics useful for purposes of this invention are also illustrated in Table 1b. Cationics useful for purposes of this invention are illustrated in Table 1c. Typically they are quaternized perfluoroalkanesulfonamidopolymethylene dialkylamines as described in U.S. Pat. No. 2,759,019.
The structures of the fluorinated synergists employed as component (B) may be chosen from compounds represented by the formula EQU R.sub.f -T.sub.m -Z
where R.sub.f is as defined above; T is R.sub.6 or --R.sub.6 SCH.sub.2 CHR.sub.1 --, m is an integer of 0 to 1, Z is one or more covalently bonded, preferably polar, groups comprising the following radicals: --CONR.sub.1 R.sub.2, --CN, --CONR.sub.1 COR.sub.2, SO.sub.2 NR.sub.1 R.sub.2, --SO.sub.2 NR.sub.1 R.sub.7 (OH).sub.n, --R.sub.7 (OH).sub.m, --R.sub.7 (O.sub.2 CR.sub.1).sub.n, --CO.sub.2 R.sub.1, --C(.dbd.NH)NR.sub.1 R.sub.2. R.sub.1, R.sub.2 and R.sub.6 are as defined above. R.sub.7 is a branched or straight chain alkylene of 1 to 12 carbon atoms, containing one or more polar groups. Preferred are compositions where Z is an amide or nitrile function. Illustrative examples of R.sub.f -synergists which can be used in the compositions of this invention are given in Table 2 and also include:
C.sub.8 f.sub.17 so.sub.2 nh.sub.2 PA0 c.sub.8 f.sub.17 so.sub.2 n(ch.sub.2 ch.sub.2 oh).sub.2 PA0 c.sub.8 f.sub.17 so.sub.2 n(c.sub.2 h.sub.5)ch.sub.2 chohch.sub.2 oh PA0 r.sub.f CH.sub.2 OH PA0 R.sub.f CH.sub.2 CHOHCH.sub.2 OH PA0 R.sub.f CHOHCH.sub.2 OH
also (C.sub.2 F.sub.5).sub.2 (CF.sub.3)C-CH.sub.2 CON(R)CH.sub.2 CH.sub.2 OH wherein R is H, CH.sub.3, C.sub.2 H.sub.5 or CH.sub.2 CH.sub.2 OH disclosed in Brit. 1,395,751; R.sub.f (CH.sub.2 CFR.sub.1).sub.m CH.sub.2 CH.sub.2 CN wherein R.sub.1 = H or F, m = 1 - 3 as disclosed in copending application U.S. Ser. No. 442952, incorporated herein by reference; and compounds of the general structure: R.sub.f --CH.sub.2 CH.sub.2 --SO.sub.x C.sub.m H.sub.2m A as described in Ger. Off. 2,344,889 wherein x is 1 or 2, R.sub.f is as described above, m is 1 to 3 and A is carboxylic ester, carboxamide or nitrile. The R.sub.f -synergists are also generally useful in depressing the surface tension of any anionic, amphoteric, or cationic R.sub.f -surfactant to exceedingly low values. Thus, R.sub.f -surfactant/R.sub.f -synergist systems have broad utility in improving the performance of R.sub. f -surfactant system in a variety of applications other than the AFFF agent systems disclosed herein.
Component (C) is an ionic non-fluorochemical water soluble surfactant chosen from the anionic, cationic or amphoteric surfactants as represented in the tabulations contained in Rosen et al, Systematic Analysis of surface-Active Agents, Wiley-Interscience, New York, (2nd edition, 1972), pp, 485-544, which is incorporated herein by reference.
It may also include siloxane type surfactants of the types disclosed in U.S. Pat. No. 3,621,917, 3,677,347 and Brit. Pat. No. 1,381,953.
It is particularly convenient to use amphoteric or anionic fluorine-free surfactants because they are relatively insensitive to the effects of fluoroaliphatic surfactant structure or to the ionic concentration of the aqueous solution and furthermore, are available in a wide range of relative solubilities, making easy the selection of appropriate materials.
Preferred ionic non-fluorochemical surfactants are chosen with regard to their exhibiting an interfacial tension below 5 dynes/cm at concentrations of 0.01 -0.3% by weight, or exhibiting high foam expansions at their use concentration, or improving seal persistance. They must be thermally stable at practically useful application and storage temperatures, be acid and alkali resistance, be readily biodegradable and nontoxic, especially to aquatic life, be readily dispersible in water, be unaffected by hard water or sea water, be compatible with anionic or cationic systems, be tolerant of pH, and be readily available and inexpensive. Ideally they might also form protective coatings on materials of construction. A number of most preferred ionic non-fluorochemical surfactants are listed in Table 3.
In accordance with the classification scheme contained in Schwartz et al, Surface Active agents, Wiley-Interscience, N.Y., 1963, which is incorporated herein by reference, anionic and cationic surfactants are described primarily according to the nature of the solubilizing or hydrophilic group and secondarily according to the way in which the hydrophilic and hydrophobic groups are joined, i.e. directly or indirectly, and if indirectly according to the nature of the linkage.
Amphoteric surfactants are described as a distinct chemical category containing both anionic and cationic groups and exhibiting special behavior dependent on their isoelectric pH range, and their degree of charge separation.
Typical anionic surfactants include carboxylic acids, sulfuric esters, alkane sulfonic acids, alkylaromatic sulfonic acids, and compounds with other anionic hydrophilic functions, e.g., phosphates and phosphonic acids, thiosulfates, sulfinic acids, etc.
Preferred are carboxylic or sulfonic acids since they are hydrolytically stable and generally available. Illustrative examples of the anionic surfactants are
______________________________________ C.sub.11 H.sub.23 O(C.sub.2 H.sub.4 O).sub.3.5 SO.sub.3 Na (Sipon ES) C.sub.11 H.sub.23 OCH.sub.2 CH.sub.2 OSO.sub.3 Na (Sipon ESY) C.sub.12 H.sub.25 OSO.sub.3 Na (Duponol QC) Disodium salt of alkyldiphenyl Dowfax 3B2 ether disulfonate Disodium salt of sulfocuc- (Aerosol A-102) cinic acid half ester de- rived from a C.sub.10-12 ethoxyl- ated alcohol Sodium Alpha olefin sulfonates (Bioterge AS-40) C.sub.11 H.sub.23 CONH(CH.sub.3)C.sub.2 H.sub.4 SO.sub.3 Na (Igepon TC42) C.sub.11 H.sub.23 CON(CH.sub.3)CH.sub.2 CO.sub.2 Na (Sarkosyl NL-97) ______________________________________
Also preferred are anionic surfactants obtained by the addition of reactive mercaptans to alkenylamidoalkane sulfonic acids, of the general structure EQU (R.sub.6 --SCH.sub.2 CHR.sub.1 CONHCR.sub.2 R.sub.3 CR.sub.4 R.sub.5 SO.sub.3).sub.m M
as described in greater detail in the copending application Ser. No. 642,270 which is incorporated by reference.
Typical cationic classes include amine salts, quaternary ammonium compounds, other nitrogenous bases, and non-nitrogenous bases, e.g. phosphonium, sulfonium, sulfoxonium; also the special case of amine oxides which may be considered cationic under acidic coniditions.
Preferred are amine salts, quaternary ammonium compounds, and other nitrogenous bases on the basis of stability and general availability. Non-halide containing cationics are preferred from the standpoint of corrosion. Illustrative examples of the cationic surfactants are
______________________________________ bis(2-hydroxyethyl)tallowamine oxide (Aromox T/12) dimethyl hydrogenated tallowamine oxide (Aromox DMHT) isostearylimidazolinium ethosulfate (Monaquat ISIES) cocoimidazolinium ethosulfate (Monaquat CIES) laurylimidazolinium ethosulfate (Monaquat LIES) [C.sub.12 H.sub.25 OCH.sub.2 CH(CH)CH.sub.2 N(CH.sub.3)CH.sub.2 CH.sub.2 OH).sub.2 ]+ (Catanac 609) CH.sub.3 SO.sub.4 [C.sub.11 H.sub.23 CONH(CH.sub.2).sub.3 N(CH.sub.3).sub.3 ].sup.+ CH.sub.3 SO.sub.4 (Catanac LS) [C.sub.17 H.sub.35 CONH(CH.sub.2).sub.3 N(CH.sub.3).sub.2 CH.sub.2 CH.sub.2 OH].sup.+ NO.sub.3 - (Catanac SN) ______________________________________
The amphoteric non-fluorochemical surfactants include compounds which contain in the same molecule the following groups: amino and carboxy, amino and sulfuric ester, amino and alkane sulfonic acid, amino and aromatic sulfonic acid, miscellaneous combinations of basic and acidic groups, and the special case of aminimides.
Preferred non-fluorochemical amphoterics are those which contain amino and carboxy or sulfo groups.
Illustrative examples of the non-fluorochemical amphoteric surfactants are:
______________________________________ coco fatty betaine (CO.sub.2.sup.-) (Velvetex BC) cocoylamidoethyl hydroxyethyl (Velvetex CG) carboxymethyl glycine betaine cocoylamidoammonium sulfonic acid betaine (Sulfobetaine CAW) cetyl betaine (C-type) (Product BCO) a sulfonic acid betaine derivative (Sulfobetaine DLH) C.sub.11 H.sub.23 CONN(C.sup.-+H.sub.3).sub.2 CHOHCH.sub.3 (Aminimides) A56203 C.sub.11 H.sub.23 CO.sup.-+NN(CH.sub.3).sub.3 (A56201) ##STR2## (Miranol H2M-SF) A coco-derivative of the above (Miranol CM-SF) Coco Betaine (Lonzaine 12C) C.sub.12-14 H.sub.25-29.sup.+NH.sub.2 CH.sub.2 CH.sub.2 COO.sup.- (Deriphat 170C) (triethanolammonium salt) ##STR3## (Deriphat 160C) ______________________________________
and the amphoterics obtained by the addition of primary amines to alkenylamidoalkane sulfonic acids, of the general structure. EQU R.sub.7 N [CH.sub.2 CHR.sub.1 CONHCR.sub.2 R.sub.3 CR.sub.4 R.sub.5 SO.sub.3]M.sub.2/n
as defined in the copending application Ser. no. 642,269, incorporated herein by reference. Component (C) surfactants also include silicones disclosed in U.S. Pat. No. 3,621,917 (anionic and amphoteric) U.S. pat. no. 3,677,347 (cationic) U.S. Pat. No. 3,655,555 and Brit. Pat. No. 1,381,953 (anionic, nonionic, or amphoteric). The disclosures of said patents are incorporated herein by reference.
A nonionic non-fluorochemical surfactant component (D) is incorporated in the aqueous fire compositions primarily as a stabilizer and solubilizer for the compositions particularly when they are diluted with hard water or sea water. The nonionics are chosen primarily on tghe basis of their hydrolytic and chemical stability, solubilization and emulsification characteristics (e.g. measured by HLB-hydrophilic-lipophilic balance), cloud point in high salt concentrations, toxicity, and biodegradation behavior. Secondarily, they are chosen with regard to foam expansion, foam viscosity, foam drainage, surface tension, interfacial tension and wetting characteristics.
Typical classes of nonionic surfactants useful in this invention include polyoxethylene derivatives of alkylphenols, linear or branched alcohols, fatty acids, mercaptans, alkylamines, alkylamides, acetylenic glycols, phosphorus compounds, glucosides, fats and oils. Other nonionics are amine oxides, phosphine oxides and nonionics derived from block polymers containing polyoxyethylene and/or polyoxypropylene units.
Preferred are polyoxyethylene derivatives of alkylphenols, linear or branched alcohols, glucosides and block polymers of polyoxyethylene and polyoxypropylene, the first two mentioned being most preferred.
Illustrative examples of the non-ionic non-fluorochemical surfactants are
______________________________________ Octylphenol (EO).sub.9,10 (Triton X-100) Octylphenol (EO).sub.16 (Triton X-165) Octylphenol (EO).sub.30 (Triton X-305) Nonylphenol (EO).sub.9,10 (Triton N-101) Nonylphenol (EO).sub.12,13 (Triton N-128) Lauryl ether (EO).sub.23 (Brij 35) Stearyl ether (EO).sub.10 (Brij 76) Sorbitan monolaurate (EO).sub.20 (Tween 20) Dodecylmercaptan (EO).sub.10 (Tergitat 12-M-10) Block copolymer of (EO).sub.x (PO).sub.4 (Pluronic F-68) Block copolymer (Tetronic 904) C.sub.11 H.sub.23 CON(C.sub.2 H.sub.4 OH).sub.2 (Superamide L9) C.sub.12 H.sub.25 N(CH.sub.3).sub.2 O (Ammonyx LO) ##STR4## (Ethomeen C/.sub.25) ______________________________________ NOTE: EO used above means ethylene oxide repeating unit. Preferred non-ionics are further illustrated in Table 4.
Component (E) is a solvent which acts as an antifreeze, a foam stabilizer or as a refractive index modifier, so that proportioning systems can be field calibrated. Actually, this is not a necessary component in the composition of this invention since very effective AFFF concentrates can be obtained in the absence of a solvent. However, even with the compositions of this invention it is often advantageous to employ a solvent especially if the AFFF concentrate will be stored in subfreezing temperatures, or refractometry requirements are to be met. Useful solvents are disclosed in U.S. Pat. No. 3,457,172; 3,422,011; and 3,579,446, and German Pat. No. 2,137,711.
Typical solvents are alcohols or ethers such as:
ethylene glycol monoalkyl ethers, diethylene glycol monoalkyl ethers, propylene glycol monoalkyl ethers, dipropylene glycol monoalkyl ethers, triethylene glycol monoalkyl ethers, 1-butoxythoxy-2-propanol, glycerine, diethyl carbitol, hexylene glycol, butanol, t-butanol, isobutanol, ethylene glycol and other low molecular weight alcohols such as ethanol or isopropanol wherein the alkyl groups contain 1-6 carbon atoms.
Preferred solvents are 1-butoxyethoxy-2-propanol, diethyleneglycol monobutyl ether, or hexylene glycol.
Component (F) is an electrolyte, typically a salt of a monovalent or polyvalent metal of Groups 1, 2, or 3, or organic base. The alkali metals particularly useful are sodium, potassium, and lithium, or the alkaline earth metals, especially magnesium, calcium, strontium, and zinc or aluminum. Organic bases might include ammonium, trialkylammonium, bis-ammonium salts or the like. The cations of the electrolyte are not critical, except that halides are not desireable from the standpoint of metal corrosion. Sulfates, bisulfates, phosphates, nitrates and the like are acceptable.
Preferred are polyvalent salts such as magnesium, sulfate, magnesium nitrate or strontium nitrate.
Still other components which may be present in the formula are:
Buffers whose nature is essentially non-restricted and which are exemplified by Sorensen's phosphate or McIlvaine's citrate buffers
Corrosion inhibitors whose nature is non-restricted so long as they are compatible with the other formulation ingredients. They may be exemplified by ortho-phenylphenol
Chelating agents whose nature is non-restricted, and which are exemplified by polyaminopolycarboxylic acids, ethylenediaminetetraacetic acid, citric acid, tartaric acid, nitrilotriacetic acid hydroxyethylethylenediaminetriacetic acid and salts thereof. These are particularly useful if the composition is sensitive to water hardness.
High molecular weight foam stabilizers such as polyethyleneglycol, hydroxypropyl cellulose, or polyvinylpyrrolidone.
The concentrates of this invention are effective fire fighting compositions over a wide range of pH, but generally such concentrates are adjusted to a pH of 6 to 9, and more preferably to a pH of 7 to 8.5, with a dilute acid or alkali. For such purpose may be employed organic or mineral acids such as acetic acid, oxalic acid, sulfuric acid, phosphoric acid and the like or metal hydroxides or amines such as sodium or potassium hydroxides, triethanolamine, tetramethylammonium hydroxide and the like.
As mentioned above, the compositions of this invention are concentrates which must be diluted with water before they are employed as fire fighting agents. Although at the present time the most practical, and therefore preferred, concentrations of said composition in water are 3% and 6% because of the availability of fire fighting equipment which can automatically admix the concentrate with water in such proportions, there is no reason why the concentrate could not be employed in lower concentrations of from 0.5% to 3% or in higher concentrations of from 6% to 12%. It is simply a matter of convenience, the nature of fire and the desired effectiveness in extinguishing the flames.
An aqueous AFFF concentrate composition which would be very useful in a 6% proportioning system comprises
Each component A to F may consist of a specific compound or mixtures of compounds.
The subject composition can be also readily dispersed from an aerosol-type container by employing a conventional inert propellant such as Freon 11, 12, 22 or C-318, N.sub.2 O, N.sub.2 or air. Expansion volumes as high as 50 based on the ratio of air to liquid are attainable.
The most important elements of the AFFF system of this invention are components (A), the fluorinated surfactant and component (B), the R.sub.f -synergist. Preferred are anionic R.sub.f -surfactants of Types A1 - A10, and A 13 as described in Table 1a, which are disclosed in copending U.S. application Serial No. 642,271. Preferred too are R.sub.f -synergists of types B1-B18, which are disclosed in part in U.S. Pat. No. 3,172,910, and which are otherwise disclosed herein.
The preferred anionic R.sub.f -surfactants, particularly in the presence of polyvalent metal ions, reduce the surface tension of the aqueous concentrate to about 20 dynes/cm. They act as solubilizers for the R.sub.f -synergists, which further depress the surface tension sufficiently that the solutions spontaneously and rapidly spread on fuel surfaces. The R.sub.f -synergists are usually present in lower concentration then the R.sub.f -surfactants and since they are polar, yet non-ionized, contribute significantly to the excellent compatibility of the subject compositions in hard water, sea water, and with ionic AFFF ingredients necessarily present.
The ionic (or amphoteric) non fluorochemical surfactants (Component C) have several functions. They act as interfacial tension depressants, reducing the interfacial tension of the aqueous R.sub.f -surfactant/R.sub.f synergist solutions from interfacial tensions as high as 20 dynes/cm to interfacial tensions as low as 0.1 dyne/cm; act as foaming agents so that by varying the amount and proportions of component (C) cosurfactant, it is possible to vary the foam expansion of the novel AFFF agent; act to promote seal persistance. By arranging the amounts and proportions of component (C) cosurfactant it is possible to a) depress the interfacial tension, b) optimize foam expansion, and c) improve seal persistance.
The nonionic hydrocarbon surfactants component (D) in the novel AFFF agent also have a multiple function by acting as solubilizing agents for the R.sub.f -surfactants (Component A) and R.sub.f -synergists (Component B) having poor solubility characteristics. They further act as stabilizing agents, especially of AFFF agent sea water premixes, influence the AFFF agent foam stability and foam drainage time, and influence the viscosity of AFFF agents, which is very critical especially in the case of 1% proportioning systems.
Solvents (Component E) are used similarly as solubilizing agents for R.sub.f -surfactants, but also act as foam stabilizers, serve as refractive index modifiers to permit field calibration of proportioning systems, reduce the viscosity of highly concentrated AFFF agents, and act as anti-freeze.
Electrolytes (Component F) generally improve the surface tensions attainable with the subject formulations; they also improve compatibility with hard water. Whereas commercial 6% proportioning AFFF agents have high solvent contents of greater than 15%, this invention also teaches the preparation of comparable formulations with excellent performance at low solvent contents.
Some of the solvents present in the formulated AFFF agents are only present because they are carried into the product from the R.sub.f -surfactant synthesis. As mentioned before other additives in the novel AFFF agent might be advantageous such as:
Corrosion inhibitors (for instance in the case where aqueous AFFF premixes are stored for several years in uncoated aluminum cans).
Chelating agents (if premixes of AFFF agents and very hard water are stored for longer periods of time).
Buffer systems (if a certain pH level has to be maintained for a long period of time).
Anti-freezes (if AFFF agents are to be stored and used at sub-freezing temperatures).
Polymeric thickening agents (if higher viscosities of AFFF agent - water premixes are desired because of certain proportioning system requirements), and so on.
Today's commercial AFFF agents are only capable of use on 6 and 3% proportioning systems. The composition of the instant AFFF agents and the ranges of the amounts of the different active ingredients in these novel AFF agents can be expressed for 0.5 to 12% proportioning systems. If the concentration in a composition for 6% proportioning is doubled then such a concentrate can be used for a 3% proportioning system. Similarly if the concentration of such a 6% proportioning system is increased by a factor of 6 then it can be used as a 1% proportioning system. As comparative data in the experimental part will show it is possible to make such 1% proportioning systems primarily:
A. Because of the higher efficiency of the novel R.sub.f -surfactants used and the smaller amounts therefore needed.
B. Because of the rather low amounts of solvents required in the new AFFF agents to achieve foam expansion ratios as specified by the military.
In the examples, references are made to specifications used by the industry and primarily the military and to proprietary tests to evaluate the efficiency of the claimed compositions. More specifically, the examples refer to the following specifications: